Waist-to-hip Ratio (WHR)

Key Points

WHR is a good measure of abdominal fat distribution, but is not a measure of absolute abdominal fat mass.

Changes in WHR with weight loss are weakly associated with changes in abdominal fat mass and health risk.

WHR, Health Risk, and Intra-abdominal Fat

Waist-to-hip ratio (WHR) is an anthropometric measure commonly used to characterize regional adiposity. WHR is a crude estimate of the relative amount of abdominal fat: the higher your waist girth compared to your hip girth, the greater your proportion of abdominal fat. As early as the 1980s, several prospective epidemiological studies reported that WHR is a significant predictor of type 2 diabetes, (1) coronary heart disease, (2) and death (3, 4). A large number of studies have since replicated these initial findings, with some reporting that WHR was a stronger predictor of myocardial infarction (5) or mortality risk (6) than body mass index (BMI) or waist circumference alone. However, this observation is not seen consistently, as most studies report that waist circumference is an equivalent, if not a superior, measure of health risk (7-11) and mortality (12-14). WHR is also reported to have a similar relationship to intra-abdominal (visceral) fat as waist circumference and BMI (15-22). Consequently, as WHR provides no clear advantage in predicting health risk, it has been suggested that waist circumference may be a more clinically useful tool because it is easier to measure.

Measuring WHR

WHR is a measure of waist circumference relative to hip circumference. Although waist circumference measurement sites vary, hip circumference is most commonly measured at the greatest protrusion of the buttocks while the patient is standing with their feet together. WHR values greater than 0.90 in men and 0.85 in women have been proposed to diagnose abdominal obesity (23). It is also possible for individuals with a similar WHR but different BMI values to have varying degrees of intra-abdominal fat.

Unlike waist circumference, WHR is not necessarily a measure of absolute abdominal fat mass. It is, however, a measure of abdominal fat relative to lower body mass. As such, a relatively lean individual could theoretically have the same WHR as an obese individual. In addition, when using WHR, it is unclear whether an individual has a high WHR due to a high waist circumference (numerator) or a small hip circumference (denominator) (Figure 1). This is important as the health risks associated with a high waist circumference, and the measures to treat them, may differ from the health risks and interventions associated with a small hip circumference. For example, individuals with a high waist girth may benefit from reducing their obesity, whereas resistance training may be better for individuals with a small hip circumference due to low muscle mass. Interpreting WHR and choosing the appropriate treatment is complicated and likely provides little insight over waist and hip circumferences alone.

One of the main limitations of WHR is its ability to predict changes in body composition or health risk. Changes in WHR could be due to changes in the numerator (waist) or denominator (hip). For example, lower WHR after an exercise intervention could be due to reductions in waist circumference or increases in hip circumference because of lower body muscle gain. Similarly, large reductions in hip circumference relative to waist circumference may cause no change in or even increase WHR despite significant weight loss and improvements to metabolic risk, particularly in women (24-26) (Figure 2). The relationship between changes in WHR and intra-abdominal fat provides further illustration of this point. Unlike waist circumference, changes in WHR do not consistently lead to changes in intra-abdominal fat, especially in women (19, 21, 27). A change or lack of change in WHR is therefore difficult to interpret. As such, waist circumference alone should be used to assess obesity, related health risk, and any changes to either.

WHR is a good indicator of health risk and an index of relative abdominal fat distribution. However, WHR is not a measure of absolute abdominal fat mass. Individuals can have varying degrees of intra-abdominal fat for a given WHR. Furthermore, WHR is often unable to detect changes in intra-abdominal fat or health risk associated with weight loss. In view of this, waist circumference alone may be a better clinical tool for assessing abdominal obesity and related health risk.

References

Ohlson LO, Larsson B, Svardsudd K, et al. The influence of body fat distribution on the incidence of diabetes mellitus. 13.5 years of follow-up of the participants in the study of men born in 1913. Diabetes 1985; 34: 1055-8.

Lapidus L, Bengtsson C and Lissner L. Distribution of adipose tissue in relation to cardiovascular and total mortality as observed during 20 years in a prospective population study of women in Gothenburg, Sweden. Diabetes Res Clin Pract 1990; 10 Suppl 1: S185-9.

1.
Ohlson LO, Larsson B, Svardsudd K, et al. The influence of body fat distribution on the incidence of diabetes mellitus. 13.5 years of follow-up of the participants in the study of men born in 1913. Diabetes 1985; 34: 1055-8.

3.
Lapidus L, Bengtsson C and Lissner L. Distribution of adipose tissue in relation to cardiovascular and total mortality as observed during 20 years in a prospective population study of women in Gothenburg, Sweden. Diabetes Res Clin Pract 1990; 10 Suppl 1: S185-9.

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